SharedRXC: A Trustless Privacy-Preserving Asset Cross-Chain Scheme by Liability Equalization

Abstract

Cross-chain technology, as a key driver for enhancing interoperability of blockchains, enables asset transfer and exchange between different blockchains. At present, cross-chain models based on light clients are widely adopted due to their fully decentralized nature and applicability to diverse scenarios. However, the rapid advancement of on-chain analysis techniques, such as address linkage and fund flow tracking, has significantly increased risks of de-anonymization in cross-chain transactions, posing serious privacy challenges. In this paper, we propose SharedRXC, a privacy-preserving asset cross-chain scheme for the light-client cross-chain model, which guarantees address unlinkability without extra privacy trust assumptions. First, to hide cross-chain addresses during interchain transmission, we propose the Ring Account (RA) to replace a single address for sending or receiving funds. In addition, we propose a zero-knowledge proof-based method to verify virtual identity ownership, allowing the virtual identity to track fund balances without exposing the addresses. Second, to prevent the exposure of the link between an address and its virtual identity caused by fund amount differences during deposits or withdrawals, which would compromise address unlinkability, we propose the Shared Burn/Mint method to obscure on chain fund change differences. Based on the liability equalization mechanism, we design two privacy-preserving cross-chain protocols: the cross-chain asset transfer (SharedRXC.T) and exchange (SharedRXC.E) protocols. Finally, we evaluateSharedRXC.TandSharedRXC.E, which reduce gas costs by 30% to 40% compared to zkCross and achieve execution times in the millisecond range. Therefore, SharedRXC provides a practical privacy-preserving solution for cross-chain financial applications in the multi-chain ecosystem.